The Tissue Culture/Monoclonal Antibody Core is an efficient, cost effective resource for the production of monoclonal antibodies (MAbs) from hybridoma cell lines, and expression of recombinant proteins from baculovirus vectors in insect cell cultures. Cell fusion and construction of new MAb secreting hybridoma cell lines has been offered as a custom service since the founding of the facility in 1988, and mass production of MAbs from large scale cultures of hybridomas was introduced as a component of the MAb service at the time of the last review. Construction of baculovirus vectors and expression of recombinant proteins in insect cells was established as a second major service over ten years ago. The usage of custom baculovirus services has continued to grow every year to become the major activity of the Core. As an additional service, the Core maintains a repository of 150 cancer cell lines in liquid nitrogen and provides UCCC investigators with seed cultures for experiments or large volume cell cultures as a source for isolation of various cell factors. The Core also maintains an On-Site Supply Center that provides commercial liquid growth media, supplements and serum at substantially reduced prices to Cancer Center Investigators. The TC/MAb core provides added value through consultation, training and quality control procedures. The Core moved to the new Fitzsimons campus in July 2004. To facilitate access to Cancer Center investigators at the 9th Avenue campus, a daily courier service for transfer of samples has been established and the On-Site Supply Center operates at both UCHSC campuses and at NJC. The TC/MAb Core is heavily used. During the last reported grant year, 115 different investigators used one or more services and the majority of users (82 or 71%) were Cancer Center members. Cancer Center users are from all 8 scientific programs and 3 consortium institutions including CU-Boulder, National Jewish Center, and CSU, and 84% hold NIH peer-reviewed funding with 31% from the NCI. The TC/MAb Core has provided support for 265 peer-reviewed publications of UCCC investigators over the last 4 years. Approximately 40% of the operating budget of the TC/MAb Core is supported by the Cancer Center Core grant, the other 60% comes from user charge-back fees. The TC/MAb Core plans to continue providing existing custom services, will expand its capacity for recombinant baculovirus production and will add a new service of down-stream processing and purification of MAbs produced in culture. To expand the capacity for baculovirus production and to add the MAb purification service, new equipment is requested over the first three years of the grant.